<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
 <head>
  <meta http-equiv="content-type" content="text/html; charset=UTF-8">
  <title>Get and/or set the current session id</title>

 </head>
 <body><div class="manualnavbar" style="text-align: center;">
 <div class="prev" style="text-align: left; float: left;"><a href="function.session-get-cookie-params.html">session_get_cookie_params</a></div>
 <div class="next" style="text-align: right; float: right;"><a href="function.session-is-registered.html">session_is_registered</a></div>
 <div class="up"><a href="ref.session.html">Session 函数</a></div>
 <div class="home"><a href="index.html">PHP Manual</a></div>
</div><hr /><div id="function.session-id" class="refentry">
 <div class="refnamediv">
  <h1 class="refname">session_id</h1>
  <p class="verinfo">(PHP 4, PHP 5)</p><p class="refpurpose"><span class="refname">session_id</span> &mdash; <span class="dc-title">Get and/or set the current session id</span></p>

 </div>
 <div class="refsect1 description" id="refsect1-function.session-id-description">
  <h3 class="title">说明</h3>
  <div class="methodsynopsis dc-description">
   <span class="type">string</span> <span class="methodname"><strong>session_id</strong></span>
    ([ <span class="methodparam"><span class="type">string</span> <code class="parameter">$id</code></span>
  ] )</div>

  <p class="para rdfs-comment">
   <span class="function"><strong>session_id()</strong></span> is used to get or set the session id for
   the current session.
  </p>
  <p class="para">
   The constant <strong><code>SID</code></strong> can also be used to
   retrieve the current name and session id as a string suitable for
   adding to URLs. See also <a href="ref.session.html" class="link">Session
   handling</a>.
  </p>
 </div>


 <div class="refsect1 parameters" id="refsect1-function.session-id-parameters">
  <h3 class="title">参数</h3>
  <p class="para">
   <dl>

    
     <dt>
<em><code class="parameter">id</code></em></dt>

      <dd>

       <p class="para">
        If <em><code class="parameter">id</code></em> is specified, it will replace the current
        session id. <span class="function"><strong>session_id()</strong></span> needs to be called before
        <span class="function"><a href="function.session-start.html" class="function">session_start()</a></span> for that purpose. Depending on the
        session handler, not all characters are allowed within the session id.
        For example, the file session handler only allows characters in the
        range <em>a-z A-Z 0-9 , (comma) and - (minus)</em>!
       </p>
       <blockquote class="note"><p><strong class="note">Note</strong>: 
        <span class="simpara">
         When using session cookies, specifying an <em><code class="parameter">id</code></em>
         for <span class="function"><strong>session_id()</strong></span> will always send a new cookie
         when <span class="function"><a href="function.session-start.html" class="function">session_start()</a></span> is called, regardless if the
         current session id is identical to the one being set.
        </span>
       </p></blockquote>
      </dd>

     
   </dl>

  </p>
 </div>


 <div class="refsect1 returnvalues" id="refsect1-function.session-id-returnvalues">
  <h3 class="title">返回值</h3>
  <p class="para">
   <span class="function"><strong>session_id()</strong></span> returns the session id for the current
   session or the empty string (<em>&quot;&quot;</em>) if there is no current
   session (no current session id exists).
  </p>
 </div>


 <div class="refsect1 changelog" id="refsect1-function.session-id-changelog">
  <h3 class="title">更新日志</h3>
  <p class="para">
   <table class="doctable informaltable">
    
     <thead>
      <tr>
       <th>版本</th>
       <th>说明</th>
      </tr>

     </thead>

     <tbody class="tbody">
      <tr>
       <td>5.0.0</td>
       <td>
        The <em>,</em> (comma) and <em>-</em> (minus)
        characters are allowed in the file session handler.
       </td>
      </tr>

     </tbody>
    
   </table>

  </p>
 </div>


<div class="refsect1 seealso" id="refsect1-function.session-id-seealso">
  <h3 class="title">参见</h3>
  <p class="para">
   <ul class="simplelist">
    <li class="member"><span class="function"><a href="function.session-regenerate-id.html" class="function" rel="rdfs-seeAlso">session_regenerate_id()</a> - Update the current session id with a newly generated one</span></li>
    <li class="member"><span class="function"><a href="function.session-start.html" class="function" rel="rdfs-seeAlso">session_start()</a> - Start new or resume existing session</span></li>
    <li class="member"><span class="function"><a href="function.session-set-save-handler.html" class="function" rel="rdfs-seeAlso">session_set_save_handler()</a> - Sets user-level session storage functions</span></li>
    <li class="member">
     <a href="session.configuration.html#ini.session.save-handler" class="link">session.save_handler</a>
    </li>
   </ul>
  </p>
 </div>

</div><hr /><div class="manualnavbar" style="text-align: center;">
 <div class="prev" style="text-align: left; float: left;"><a href="function.session-get-cookie-params.html">session_get_cookie_params</a></div>
 <div class="next" style="text-align: right; float: right;"><a href="function.session-is-registered.html">session_is_registered</a></div>
 <div class="up"><a href="ref.session.html">Session 函数</a></div>
 <div class="home"><a href="index.html">PHP Manual</a></div>
</div></body></html>
